Although considered undersized to play defensive end in the NFL, a fact that was pointed out by Mel Kiper during ESPN's coverage of the 1989 NFL Draft, Lageman was taken in the first round by the New York Jets, much to he dismay of Jets fans, and the derision of fans of other NFL teams, as seen at the draft. Lageman's NFL career spanned 10 seasons, the first six with the Jets, and the final four with the Jacksonville Jaguars.[1] His best year came in 1991 when he made ten quarterback sacks. He made a career total of 47 sacks in the NFL.

Lageman's playing career ended on the first game of the 1998 season in Chicago. Although the Jaguars won on a last second touchdown pass from Mark Brunell to Jimmy Smith, they lost Lageman to a torn muscle in his arm. He never played again.

During his time in Jacksonville, Lageman, an avid hunter and fisherman, began his broadcasting career with a radio show titled "The Outdoors Show" along with Captain Kevin Faver and Captain Kirk Waltz. After his playing career, Lageman continued his broadcasting career as a football color analyst on Fox television. By 2001, "The Outdoors Show" had moved from an all-sports station (WBWL-AM) to a 50,000 watt news-talk station (WOKV) and soon after, Lageman joined the play-by-play man Brian Sexton in the booth of the Jaguars Radio Network as the color analyst. He also serves as co-host of the weekly "Jaguars This Week" radio show along with Sexton, Jaguars.com senior writer John Oehser and former Jaguars teammate Tony Boselli, and is a castmember of the weekly television program, Jaguars All Access.